


RIVETALE

by risaXrisa



Category: Undertale (Video Game)
Genre: AU, Alternate Universe, Rivetale, Rivetale AU, Undertale AU, Undertale Pacifist Route
Language: English
Status: In-Progress
Published: 2016-09-10
Updated: 2016-09-12
Packaged: 2018-08-14 04:05:26
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 4,106
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7997929
Author URL: https://archiveofourown.org/users/risaXrisa/pseuds/risaXrisa
Summary: <blockquote class="userstuff">
              <p>After the end of the true pacifist route something peculiar happens, and Frisk falls into the Underground once again. But something is seriously wrong. Everyone and everything is in fragments, the world a broken greyscale mess of what Frisk has come to know. The void is slowly consuming everything. Frisk soon encounters W.D. Gaster, fully formed, and the only ‘whole’ being. As for all the other monsters, their souls were unable to take the strain, and thus scattered across the underground in pieces. Gaster enlists the help of Frisk to gather the pieces, and make everyone whole once more. With the world a mere echo of its former self can Frisk piece everyone they hold dear back together, and save them all before the void consumes everything?</p><p>[[INDEFINITE HIATUS]]</p>
            </blockquote>





	1. The Underground’s Collapse

**Chapter 1: The Underground’s Collapse**

“What … what’s happening?”

It was dark, way too dark for Frisk’s liking, and the familiar sense of falling wasn’t helping to quell their racing thoughts. The last thing they could remember was falling asleep on the couch. They had been watching television with their friends, after filling up on a delicious dinner that both Toriel and Papyrus prepared. No. No it couldn’t be. They couldn’t be resetting again could they?! The thought alone made them want to scream out.

Why? Why did it have to reset? Finally everyone was happy. All the monsters had returned to the surface. Frisk finally had a home, a loving family, friends who cared about them … why did it all have to be taken from them now?! It wasn’t fair!

Suddenly Frisk landed with a thud, the back of their head smacking against the ground, and they let out a small cry of pain. That certainly hurt more than it ever did before. Usually the flowers cushioned their fall a small bit. Wincing, they sat upright, still slightly dizzy from the impact. Frisk blinked a few times in an attempt to clear their vision of the black and grey blurs surrounding them, but something was off. Had they really hit their head that hard?

They resorted to shaking their head, hoping that would help their sight return to normal, but still it did not clear up. When Frisk turned their gaze to the ground they quickly realized that their eyesight was just fine. Crushed underneath their small body, where a bed of golden flowers usually grew, were grey and white ones instead. Frisk couldn’t help but swallow as a feeling of nervousness started to take over.

If they took a closer look, small cracks could be seen running through the various stems and petals, some of the parts crumbling off entirely just to float near where they had fallen. Other parts had just vanished entirely, as if they had just faded away.

With a slight wince Frisk stood, and took a better look around. What happened here? This definitely wasn’t the Underground they had come to know and love. Every single thing was colored in greyscale, and looked as if it was deteriorating into nothing. Just like the flowers underfoot, pieces of the Ruins, the ground, even the interior of the mountain itself, held so many cracks. The pieces that had broken off floated about eerily, scattered around like dust.

Frisk’s brows furrowed, and they gripped at the front of their shirt, hand clenching tightly around the fabric. Seeing the Ruins like this was deeply unsettling. Something was seriously wrong, and they were determined to find out why.

They broke into a sprint, following the familiar, but now broken path. Everything was so different, and it almost made them want to cry. What if it wasn’t just the Ruins? If the whole Underground was like this then what had become of their friends? The thought alone made a surge of pain flicker through their soul. No. They had to keep their hopes alive … if not for themselves then at least for their friends. That’s what they would’ve wanted Frisk to do after all.

Noticing a small flicker of light hovering above the ground a few steps ahead they stopped. They couldn’t help but remember that this was the spot where they had first met Flowey. Just ahead was where Toriel had first appeared as well. The same exact place the light was floating above.

It was almost as if it was calling to them, and Frisk approached slowly. After observing it for a brief moment they got to their knees, and reached a shaky hand out to touch it, their soul pounding in their chest. Just as the tip of their finger brushed against it a familiar voice rang throughout their mind.

‘Did you just call me … Mom?’

It was just a sentence, a beloved memory of words spoken, but it sent a shiver down their spine nonetheless. There was no mistaking that soft motherly voice. Was this … a piece of Toriel’s soul? No.

“How can that even be possible? Monster souls … ”

“Are not supposed to last outside of death, right?” A deep voice echoed throughout the room, interrupting Frisk’s train of thought. “Well under normal circumstances you would be correct.”

Frisk’s head slowly rose up to meet the eyes of a very tall figure, their own eyes widening. They had never seen this monster, but couldn’t shake the feeling they had met somewhere before. The entirety of the stranger was outfitted in black clothes, save for the grey turtle-neck sweater they wore underneath. A thin pair of glasses sat on his face and behind them were deep black sockets, hauntingly similar to Sans’. But unlike Sans this monster had glowing purple dots for pupils, and his eyes were currently locked on Frisk.

The monster reached down and offered his hand. Frisk was hesitant at first, noticing the large hole in his palm, but decided to go ahead and accept his kind offer. The tall monster effortlessly helped them to their feet, and Frisk brushed off their knees, before looking back up at him.

“It is very surprising to see you here. I never expected you would find your way to this timeline.” He spoke with a small smile, but to Frisk it seemed somewhat sad. Considering the surrounds, he obviously had a right to be.

“Wait … do you know me?” Frisk asked, a confused expression donning their face. Granted, this monster looked familiar, but they were certain they hadn’t met before.

“Oh, my apologies. I inaccurately assumed you would remember me from our brief interaction in Waterfall.” He replied with a slight chuckle, reaching a hand around to rub at the base of his head. “I am W.D. Gaster, royal scientist of the Underground. It is nice to formally meet you, Frisk.”

Wait a minute. Now that Frisk thought about it he did look strangely similar to a monster they had encountered in Waterfall, although it had been entirely by accident. They had stumbled upon a hidden room, only to find a monster clad in black inside, but they had disappeared before Frisk even got a chance to say hello. Was that him, but in this timeline? And did that mean he remembered the resets as well?

“That was you in the hidden room?” Frisk questioned, a glimmer of curiosity shinning in their eyes.

Gaster gave them a curt nod of approval, confirming their suspicions to be true. “Yes. Well … a different version of me, that is.”

“So you remember the resets? Like Sans and Flowey?”

“And, do not forget, yourself.” He smiled, moving his hands to rest in the pockets of his long black coat. “I am terribly sorry you have to see everything as it is. It must be hard when you are so used to everything looking more … bright.”

Desperate for some kind of answer, they turned their eyes back down to look at the small piece of Toriel’s soul. “What happened here?” Frisk asked, their tone almost pleading.

Gaster followed Frisk’s line of sight, and let out a small sigh. It was a reasonable, and quite obvious question, but it would take some time to explain everything and he would rather not do that here. Besides, he needed to know something first. If Frisk was able to touch the soul fragment, maybe there was a chance.

“I will be happy to explain everything in due time, but first I have a request to ask of you.” He spoke, reaching into his jacket to pull out a small glass container, before placing it into Frisk’s hands. “Do you think you could try placing the soul fragment in this?”

Frisk arched a single brow. A part of them was upset that they weren’t getting the answers right away, but the other half wondered why he would even ask such an odd request. But they figured it couldn’t do any harm. What did they have to lose? Frisk gave him a curt nod and kneeled down once more, gently cupping the glowing fragment in their hands. They placed it softly into the container, shutting the lid, and watched briefly as it hovered in place. Frisk stood, looking back up at Gaster. His eyes, no his entire demeanor, seemed to light up at the small action. Was this really that important?

“Finally … ” He smiled brightly, a look of hope slowly rising to his features. He seemed to be speaking more to himself than to the human who stood before him, and Frisk cocked their head in confusion. “This means that there is still a chance to save this world … to save everyone!” He exclaimed.

Frisk’s heart skipped a beat at those words. Was there really a way to turn everything here back to normal? If so then maybe there was also a chance they could get back to their own timeline … to their happy ending. Frisk wasn’t exactly sure what they could do, but they certainly weren’t going to stand idly by while this world fell apart at the seams.

Gaster held his hand out to them once again, but this time it was far less solemn. He even looked a bit excited. “Please, will you come with me, Frisk?” He asked, grinning from non-existent ear to ear. “There is so much work that needs to be done. I could use your help.”

The look on Gaster’s face … it quickly filled Frisk with determination. If there was even the tiniest bit of a chance they could help put this world back in order then Frisk was going to do whatever they needed to. Without a second thought, Frisk promptly took his hand with a look of resolution, holding the container to their chest with their free arm.

They nodded, and suddenly they disappeared on the spot, leaving only a brief black cloud behind as Gaster teleported them away.

 

**A/N: Welcome to RIVETALE! First chapter is finally done. *collapses on keyboard* For me the first one is always the hardest, but I’m happy with how it turned out. This all originally started as just a fanfiction AU, but really it has become something much more to me. I plan on posting all of my Rivetale character designs in the near future, and they can be found at rivetale.tumblr.com. The other chapters will be longer than this one, mainly because this one was just to get things started up. I hope you enjoy~! Thanks to my awesome beta reader sinfreeamythyst. You’re the best! Please leave comments. I'd like to hear what you all think c:**


	2. Time of Enlightening

**Chapter 2: Time of Enlightening**

The trip through the void was as unpleasant as usual. Frisk had almost forgotten to hold their breath, having traveled through the black empty expanse with Sans only a few times before. The void almost seemed alive, reaching out in an attempt to suck in whatever glimmer of life came traveling through it. When the two suddenly appeared in a familiar, albeit dimly lit, laboratory, Frisk sucked in a deep breath, clutching at the container still held against their chest, and took a look around. This was the lab tucked away behind the skeleton brothers’ house, although it looked much more lived in. There was even a set of stairs going downward in the far side of the lab, behind a machine that was covered with a tarp.

“There we go.” Gaster smiled down at them, letting go of their hand, and snapping his fingers. The lights instantly brightened around them, and Frisk had to blink a few times to adjust to the sheer whiteness of the room. “Much better. I take it you still remember this place?”

Frisk nodded. “Yeah, but I only came here once. Something about it just … unnerved me I guess.”

“Yes, I suppose my lab can be quite unsettling to most. I do apologize for that.” He smiled sadly, and removed his coat, hanging it on a nearby hook. “But then again I believe the same could be said about most laboratories.”

“So this place is yours?” Frisk questioned, looking around more, until they were hit by a sudden realization. “Wait … then that means you must know Sa-”

“The container if you please?” Gaster quickly cut them off, nonchalantly brushing the unfinished statement aside.

He turned around, and held out his hand, acting as if he hadn’t done anything out of the ordinary. Frisk was young, but they weren’t dumb. They knew when a topic was intentionally being avoided, but if Gaster didn’t feel comfortable enough talking about it then they weren’t going to pressure him. After all it was his business and they had no right to but their nose into it.

Frisk nodded, holding the container out to him, and he easily picked it up with one hand, placing it atop a black shelf. He seemed to stare at the piece for a short moment, contemplating what Frisk had no clue, but he almost looked relieved. With a swift turn Gaster faced them once again.

“I believe that I still owe you an explanation.” He sighed, picking up a nearby chair and placing it in front of his own. “Please, take a seat.” He motions, seating himself down in his own chair.

Frisk promptly hopped up on the offered chair. It was a little tall, but nothing they couldn’t manage. Once they were seated comfortably they faced the tall monster, whose expression started to grow somber. The silence carried on for a brief moment, before Gaster finally broke the silence.

“I suppose I should just start from the beginning, yes?” He spoke lowly, rubbing the back of his head. He took a deep breath, and gathered his thoughts. He hadn’t spoken to anyone in such a long time, much less about why this timeline was the way that it was. “You are aware of our history, or at least the basic premise of it. Long ago humans sealed us here under the mountain, but their magicians … their magic was unstable. Humans have never been very gifted with it, so they knew very little about the powers that could be unleashed.”

“So humans CAN use magic?” Frisk asked, tilting their head.

Gaster nodded. “Yes, but it is very rare for a human to possess the abilities. Statistically speaking maybe one out of a hundred-million at best, but it does happen and when it does the magic is very unstable. Needless to say, the humans gathered every magician available at that time. With their combined efforts they were able to drive us underground, but … ” He paused, glancing down at his hands that had begun to fiddle with the hems of his sleeves. “In the process of doing so they made a crack in our new cut-off world. A crack in the timeline. Over time that crack grew, and thus the void began to seep through.”

Frisk’s breath caught in their throat. The void was bad enough traveling through, but to have it spill out into the Underground? That was almost unfathomable. No wonder the world was in such a mess. Their eyes met Gaster’s, and quickly noticed his had turned sad once again. How long had he lived down here with the world in this state? How long had he gone without seeing or speaking with a fellow monster? Frisk could only imagine the loneliness the man endured. Having to watch all your friends fall to pieces around you? But he had stayed strong for all this time. Frisk wasn’t sure they could’ve handled it.

“The void is very hard to explain. I wish I knew more about it, but the science is near impossible to figure out.” Gaster sighed, and Frisk reached forward, patting his hands gently, silently urging him to continue. He gave them a small smile in return. “It began to consume everything. Unable to take the strain the monsters’ souls were spread out in pieces all across the Underground. For the longest time I have been trying to figure out a way to return everything to what it once was. The only thing I have not been able to conclude is what would happen if the souls were put back together? My theory is that until all the souls have been put back together the void cannot be shut.”

“Is there a reason why you can’t pick up the pieces?” Frisk questions, looking over to the piece of Toriel’s soul on the shelf.

“I wish I knew, and believe me I have certainly tried. Perhaps it is my connection to the void?” Gaster reached up, and adjusted his spectacles. “I am unable to touch them, much less pick them up. They just seem to faze right through me. I suppose with you it has something to do with the fact that you are human. Your soul is much more durable than a monster’s, and you have a stronger physical form as well. That is why I need your help.”

“I guess that makes sense.” Frisk replied. Truth was anything to do with science went over their head, but Gaster seemed to know what he was talking about. He had been around it for a long time. Just as Frisk was about to question him about how he was connected to the void he spoke up again. Could he read their mind, or was it just coincidence?

“If you do not mind my asking … how did you come to find the soul piece, Frisk?” He asked, a very curious expression masking his face. “Did you just happen upon it while you were following the path?”

“Well yes, and no.” They replied. “It was kind of like it’d called out to me, but … to my soul? And when I touched it I heard Toriel’s voice in my head. It was something she said when we first met, but it was too real to be just a memory.”

“Hmm.” Gaster thought to himself, rubbing his chin in contemplation. “That does seem strange, but given your history with the timelines it is not very surprising. In all honesty it could prove useful in finding the more difficult pieces. Are you certain you are up to the task, Frisk? It will take a long time to gather all the souls, and put them back together.”

Frisk nods. They are filled with the determination to save their friends, and the fact was plainly evident on their face. It was the only confirmation Gaster needed. He smiled, before spinning his chair around to dig through the bottom drawer of his desk, pulling out a watch-like device. He turned back to Frisk, and attached it around their wrist.

“I designed this a long time ago for … well that does not matter now, but it will allow you to teleport back and forth to the lab whenever you need to drop off a new soul piece.” He spoke, standing from his seat. “It is very simple to use. All one needs to know is where they wish to go. I suggest you give it a test run. Try teleporting into the house. I trust you remember what the living room looks like?”

“Yeah.” Frisk nodded.

“Good.” He smiled, placing his hands in his pockets. “Now give it a try. Close your eyes, and paint a clear picture in your mind. I will meet you there.”

Frisk followed his instructions, closing their eyes tightly, as their brows furrowed in concentration. They pictured the worn out green couch, the television, the stairs, and the table with the infinite quantum physics joke book. They pictured every detail they could remember. After a few moments Frisk wasn’t sure how long they’d have to keep painting this mental picture, but they didn’t want to open their eyes too early and risk messing up.

A deep chuckle rang through Frisk’s ears. “You can open your eyes now.”

Frisk did just that, and their mouth hung open slightly. It had actually worked … they were in Sans and Papyrus’ house! Wait … wouldn’t it also be Gaster’s house as well? Seeing as though it was his lab they had previously been in. They looked up at the tall monster, and gave him a soft smile which he returned. He obviously looked pleased.

“That was very well done. I was not sure if a human would even be able to use the device.” He grinned. “You never cease to amazing me, Frisk.”

“I’ll take that as a compliment.” Frisk laughed bit, running a hand through their hair.

“Now that we have gotten that out of the way I suggest you eat something, and get a good night’s sleep. There is an assortment of foods in the refrigerator. I would offer to cook you something, but my skills in the kitchen are far under subpar.” He spoke, walking over to the linen closet, retrieving a blanket and pillow for Frisk to sleep with.

“You mean to say you’re a terrible cook?” Frisk jokes, earning a sheepish smile from the monster.

“That would be a grave understatement, but I am certain you would be far more capable than I ever would.” He chuckled, placing the bundle atop the couch. “Now I must return to my lab. There is much to be worked on, before we begin our work.” He reaches down, and ruffles Frisk’s messy hair. “I bid you a goodnight, Frisk. Sleep well.”

“Goodnight, Gaster.” Frisk smiled, giving him a small wave, as he promptly teleported away.

Now that they were alone Frisk decided to take a walk around the house, and see just how different everything was. Aside from the cracks and everything being colored in gradients of grey, white, and black very little had changed from the immediate looks of it. They walked into the kitchen, and a small frown graced their lips. The sink was … normal. Still they looked beneath it, but there were no bones, and of course no annoying dog. They opened the fridge and instead of a spaghetti museum there were just various other foods. They found that they really weren’t in the mood to eat right now.

With a sigh they walked back to the living room, glancing over at the table where Sans’ pet rock usually sat. It wasn’t there. They looked beside the television, hoping to see the punny skeleton’s sock, and a series of sticky notes made by both brothers. It wasn’t there either. Frisk began to make their way upstairs. Why were all the little things missing? Sure, they probably weren’t very important to most, but they meant the world to Frisk. It was what made this house a home after all.

Frisk turned the knob to Papyrus’ door, and peeked inside the room, letting out a slightly relieved breath. Everything still looked the same, although it still lacked color. They walked inside and stared down at the energetic skeleton’s bed-car. He really did love this thing, especially in their timeline where he got to drive it around the surface like he always dreamed. The thought brought tears to Frisk’s eyes, and they quickly walked out of the room.

Without even thinking about it they headed in the direction of Sans’ room, and opened the door. Thankfully it was unlocked. As always it was a mess, but sadly no tornado of garbage was flying around in the corner. Frisk placed their hand on the doorframe, clenching their teeth as they tried desperately to fight off the tears. They just couldn’t get up the nerve to walk inside, and that hurt even more.

Frisk slowly make their way back downstairs, and got comfortable on the couch, wrapping the thick blanket around them, snuggling as deep as they could into it. It smelled like Papyrus and Sans’, and immediately their resolve broke down all at once. The unshed tears fell down their face in droves, dampening the pillow, as they tried to muffle their cries.

They would put everything back to the way it should be. No matter what it took, no matter how long, they would set things right. They had to.

 

**A/N: Well here you all go. The second chapter is finished. Honestly, I didn’t think I would be getting this much of a response, but I am happy you all seem to like it so far. Please let me know what you all think. I’d love to hear feedback from you guys, so please leave a comment. Thanks again to my awesome beta reader sinfreeamythyst. As always feel free to check out rivetale.tumblr.com for more shenanigans concerning Rivetale~! c:**


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